Thank you very much for the most elegant and concise way of determining the characteristic impedance of a transmission line! Other people's solutions involved way too much math. With your method, I was able to quickly and easily confirm that a nice and inexpensive "supposed" RG316 coax was actually 50 Ohms impedance, and some of my old coax was about 75 ohms, which I expected but used as a test to ensure I was doing it right. This has releived so a chunk of frustration. Thank you again! -VK4SSE, Rob
Stu, thanks for another instructive video about using the nano. I liked how that sneaky "4" jumped into your formula to suggest that the cable was 300 ohms; another common type. Keep 'em coming and 73.
Yeah, those 4s get me every time... I think we will do some more Oscilloscope stuff. Then take a poke at the Spectrum Analyzer. Thanks for your comments! Stu AG6AG
This is good. Works for twisted pairs too (sometimes important when winding baluns). There are a few other methods for measuring cable impedance. One of my favorites is to put a potentiometer at the end of the cable and reduce the circle to a dot. The pot resistance is the impedance. The open/short method is also popular. For typical coax, just measuring the capacitance per foot is quick and dirty. There are tables showing capacitance for a given coax impedance. For cables with a sudden change in impedance (bad shield or splice) the TDR method is best for me. I can see the impedance vs length (requires a fast rising pulse and oscilloscope). For a real challenge use wire that is lossy (nickel wire or very small gauge wire). : )
bang on timing there Stu, i am about to buy a nano vna off of a local amateur sale site close to me, and as you have been spot on with the log4om v2 videos for easy setup, and i have reffered to you videos for mine & a friends setup, this video could not have been better timing, as i have numerous bits of coax that could do with testing,Thanks in Advance Stu
Thanks for the info, Stu! I just bought a nanovna h4 and trying without much success how to decode the menu to do the coax length. Good explanation (since I don't have the software for it yet...)! Gonna download this video for reference until I get more time in on the nano...
Good video Stu. I have always used MFJ 269 to test and find out the length or broken point, but your video shows how it can be calculated using nano VNA. Very informative. I guess you have a 4" screen version of it for the video. Mine is the smaller version and I often have hard time reading it.
WAIT you said you hooked the coax to the nano vna, but is there a load or any thing on the other end of the coax? When i hook my coax up my little circle is as big as the largest circle on the smith chart ....
Hi Robert, Yeah I hid that statement away in the calculator part of the video. Here is where I give away that there is a 50ohm dummy load on the end of the coax. ruclips.net/video/ORaYx9ab6zg/видео.htmlsi=ZJMZBp4u-nw8KCan&t=455 Sorry for the confusion, Stu AG6AG
could you not try the measurement by plugging a 50 ohm dummy load on the other end ?? to do the measurement with for distance, just a thought Stu, good video Stu keep them coming :)
Hi Kevin, You can do the measurement with the far end either shorted or open. I don't think you could accurately measure the distance with a 50 Ohm load on the end. You certainly could try it, but I think the measurement would be a bit off... My next project related to the coax length is to try measuring a coax with an antenna on it to see if there is a bump where the connector to the antenna itself is. In theory, the big jump will be at the end of the antenna, but I think I will still see a small jump at the connector at the end of the coax. If you test it with a 50 Ohm load on the end let me know your results! Stu AG6AG
Thank you very much for the most elegant and concise way of determining the characteristic impedance of a transmission line! Other people's solutions involved way too much math. With your method, I was able to quickly and easily confirm that a nice and inexpensive "supposed" RG316 coax was actually 50 Ohms impedance, and some of my old coax was about 75 ohms, which I expected but used as a test to ensure I was doing it right. This has releived so a chunk of frustration. Thank you again! -VK4SSE, Rob
Glad it made it a little easier!
Stu
AG6AG
What is that cool calculator that you are using? Great video have learned a lot from it and will watch several times again.
That is an Android app called Panecal Plus. It's a great scientific calculator.
Stu
AG6AG
A great informative video, Stu. 😊Thanks & 73's de Glenn DL8FG/WB5FDJ
Glad you liked it!
Stu
AG6AG
Stu, thanks for another instructive video about using the nano. I liked how that sneaky "4" jumped into your formula to suggest that the cable was 300 ohms; another common type. Keep 'em coming and 73.
Yeah, those 4s get me every time... I think we will do some more Oscilloscope stuff. Then take a poke at the Spectrum Analyzer.
Thanks for your comments!
Stu
AG6AG
I'm working on a project and this was very helpful. Thanks!
Glad it was helpful!
Stu great educational video. I use nano all the time but this is some new to try....thanks
Hi Tom,
Glad you enjoyed it! I have to admit I'm constantly surprised as to what this little $100 thing can do.
Stu
AG6AG
This is good. Works for twisted pairs too (sometimes important when winding baluns).
There are a few other methods for measuring cable impedance. One of my favorites is to put a potentiometer at the end of the cable and reduce the circle to a dot. The pot resistance is the impedance.
The open/short method is also popular. For typical coax, just measuring the capacitance per foot is quick and dirty. There are tables showing capacitance for a given coax impedance.
For cables with a sudden change in impedance (bad shield or splice) the TDR method is best for me. I can see the impedance vs length (requires a fast rising pulse and oscilloscope).
For a real challenge use wire that is lossy (nickel wire or very small gauge wire). : )
Good points. Thanks for posting!
Stu
AG6AG
bang on timing there Stu, i am about to buy a nano vna off of a local amateur sale site close to me, and as you have been spot on with the log4om v2 videos for easy setup, and i have reffered to you videos for mine & a friends setup, this video could not have been better timing, as i have numerous bits of coax that could do with testing,Thanks in Advance Stu
Glad it is helping!
Stu
AG6AG
Thanks for the info, Stu! I just bought a nanovna h4 and trying without much success how to decode the menu to do the coax length. Good explanation (since I don't have the software for it yet...)! Gonna download this video for reference until I get more time in on the nano...
Glad I could help! Make sure you report back and let me know if you have any other questions!
Good video Stu. I have always used MFJ 269 to test and find out the length or broken point, but your video shows how it can be calculated using nano VNA. Very informative. I guess you have a 4" screen version of it for the video. Mine is the smaller version and I often have hard time reading it.
WAIT you said you hooked the coax to the nano vna, but is there a load or any thing on the other end of the coax? When i hook my coax up my little circle is as big as the largest circle on the smith chart ....
Hi Robert,
Yeah I hid that statement away in the calculator part of the video. Here is where I give away that there is a 50ohm dummy load on the end of the coax.
ruclips.net/video/ORaYx9ab6zg/видео.htmlsi=ZJMZBp4u-nw8KCan&t=455
Sorry for the confusion,
Stu
AG6AG
ok thanks NS9T@@AG6AG
What's the calculator you use? I like it!
Hi-
Panecal calculator program for Android. I love it!
Stu
could you not try the measurement by plugging a 50 ohm dummy load on the other end ?? to do the measurement with for distance, just a thought Stu, good video Stu keep them coming :)
Hi Kevin,
You can do the measurement with the far end either shorted or open. I don't think you could accurately measure the distance with a 50 Ohm load on the end. You certainly could try it, but I think the measurement would be a bit off...
My next project related to the coax length is to try measuring a coax with an antenna on it to see if there is a bump where the connector to the antenna itself is. In theory, the big jump will be at the end of the antenna, but I think I will still see a small jump at the connector at the end of the coax.
If you test it with a 50 Ohm load on the end let me know your results!
Stu
AG6AG